The present disclosure relates to a photosensitive member refreshing device and an image forming apparatus.
A photosensitive drum (photosensitive roller) in an electrophotographic image forming apparatus has a photosensitive layer on a surface thereof. Photosensitive layers are categorized as organic photosensitive members, selenium arsenic photosensitive members, amorphous silicon photosensitive members, or the like according to their principal components. The organic photosensitive members are relatively inexpensive but need to be replaced frequently as being susceptible to wear. The selenium arsenic photosensitive members have a longer life as compared with the organic photosensitive members but are difficult to handle as including a toxic substance. The amorphous silicon photosensitive members are harder, more resistant to wear deterioration, and easier to handle as being harmless substances. Therefore, amorphous silicon photosensitive drums are insusceptible to deterioration of properties of their photosensitive layers and allow maintenance of high image quality even after prolonged usage. Thus, the amorphous silicon photosensitive members are advantageous in terms of environmental friendliness and prevention of cost increase, and therefore the demand for amorphous silicon photosensitive drums has been increasing recently.
Meanwhile, photosensitive drums can be a cause of a phenomenon referred to as image deletion. The image deletion is the phenomenon that describes occurrence of a blurred image or an edge stagnant image. The image deletion occurs because discharge products such as a nitric acid ion and an ammonium ion produced through discharge from a conductive member attach to a surface of a photosensitive drum, and the discharge products are ionized in a high humidity environment to partially reduce the surface resistance of the photosensitive drum. An electrostatic latent image formed on a film having a reduced surface resistance runs outward to cause potential drop. As a result, the boundary of the electrostatic latent image becomes unclear, leading to the image deletion.
The image deletion occurs pronouncedly in an image forming apparatus including an amorphous silicon photosensitive member. This is because the amorphous silicon photosensitive member has a surface that is insusceptible to wear with a blade (cleaning blade) or the like, and the surface easily absorbs moisture.
In a known technique, therefore, aging is performed on a photosensitive drum prior to image formation in order to prevent the image deletion. The aging is to grind and remove discharge products deposited on the surface of the photosensitive drum. Some image forming apparatuses vary the duration of the aging according to the degree of the image deletion.